1,912 research outputs found
Defect behavior in electron-irradiated boron- and gallium-doped silicon
Production and anneal of defects in electron-irradiated, float-zone silicon solar cells were studied by DLTS. In boron- and gallium-doped, n+-p cells, dominant defects were due to the divacancy, carbon interstitial, and carbon complex. Results suggest that the DLTS peak normally ascribed to carbon complexes also involves gallium. For gallium- and, to a lesser extent, boron-doped samples, damaged lifetime shows substantial recovery only when the carbon-complex peak has annealed out at 400 C. In boron-doped, n+-p-p+ cells, a minority carrier trap (E1) was also observed by DLTS in cells with a boron p+, but not in those with an aluminum p+ back. A level at Ev + 0.31 eV appeared upon 150 C annealing (E1 out) in both p+ back types of samples
Cloning, Sequencing, and Characterization of Luciola italica Luciferase
The characteristic yellow-green light of a firefly is the result of a multi-step reaction catalyzed by the luciferase enzyme. This enzyme has many applications in the biomedical field and ongoing work is being done to alter its properties to better fit these applications. The purpose of this project was to clone the Luciola italica luciferase cDNA and to express, purify and fully characterize the corresponding bioluminescence-catalyzing enzyme in hopes of obtaining novel bioluminescent materials. Fireflies were collected in the countryside of Bologna, Italy, flash frozen in liquid nitrogen and total RNA was extracted from the firefly lanterns. The L. italica luciferase cDNA was successfully cloned by RT-PCR using a gene-specific primer set based on the DNA sequence of the Eastern European Luciola mingrelica luciferase gene. The L. italica cDNA was determined to be 1647 base pairs in length with an open reading frame of 548 amino acids. Initial characterization of the enzyme showed that the L. italica protein exhibits bioluminescent activity similar in intensity to the common North American Photinus pyralis luciferase; however it produces light that is slightly red-shifted (having maximum emission at 564 nm). By steady state kinetics analysis, the L. italica Km for LH2 was found to be 0.095 mM, and that of P. pyralis is 0.015 mM. On the converse, both enzymes had similar Km values for Mg-ATP (0.160 mM for P. pyralis and 0.180 mM for L. italica). The L. italica enzyme was found to sustain its light in the visible region for a longer period of time than the P. pyralis enzyme. Phylogenetic analysis showed that the L. italica luciferase gene has 95.8% and 95.6% amino acid sequence identity to the Hotaria unmunsana (Korea) and Hotaria parvula (Japan) luciferase proteins, respectively. The processes that were used to clone the Luciola italica luciferase gene, characterize the protein, and optimize protein growth conditions ar
HiMAT flight program: Test results and program assessment overview
The Highly Manueverable Aircraft Technology (HiMAT) program consisted of design, fabrication of two subscale remotely piloted research vehicles (RPRVs), and flight test. This technical memorandum describes the vehicles and test approach. An overview of the flight test results and comparisons with the design predictions are presented. These comparisons are made on a single-discipline basis, so that aerodynamics, structures, flight controls, and propulsion controls are examined one by one. The interactions between the disciplines are then examined, with the conclusions that the integration of the various technologies contributed to total vehicle performance gains. An assessment is made of the subscale RPRV approach from the standpoint of research data quality and quantity, unmanned effects as compared with manned vehicles, complexity, and cost. It is concluded that the RPRV technique, as adopted in this program, resulted in a more complex and costly vehicle than expected but is reasonable when compared with alternate ways of obtaining comparable results
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Traumatic Bone Bruises in the Athlete’s Knee
Context: Mobile water within the bone marrow is a physiological phenomenon that is identifiable on magnetic resonance (MR) imaging, and signal changes can result from blood pooling, reactive hyperemia, edema, and microfracture. When these MR lesions are associated with an acute traumatic event, the findings are referred to as bone bruises and so represent a unique manifestation of injury. This review discusses bone bruises in anterior cruciate ligament (ACL) tears, patella dislocations, occult fractures, and contusions. Methods: A PubMed search of the literature from 1982 to December 2009 was conducted with the terms knee and bone bruise. Results:: Bone bruises are associated with ACL tears, patella dislocations, occult fractures, and contusions. For each injury, a unique pattern of bone bruising is found on MR imaging, which results from the acute trauma. When acute trauma produces a subchondral lesion with low T1-weighted and high T2-weighted signal intensity, the resulting bony contusion is best described as a bone bruise. Conclusions:: Bone marrow edema is identified using MR imaging and may result from traumatic or atraumatic causes. Bone bruises can be characterized by their pattern at presentation, by the mechanism of injury, and by their associated injuries. This type of bone edema can accompany contact and noncontact ACL ruptures as well as patella dislocations. Although increased marrow edema can be associated with an occult fracture, the long-term significance of these lesions is unclear
Normal Mode Determination of Perovskite Crystal Structures with Octahedral Rotations: Theory and Applications
Nuclear site analysis methods are used to enumerate the normal modes of
perovskite polymorphs with octahedral rotations. We provide the modes
of the fourteen subgroups of the cubic aristotype describing the Glazer
octahedral tilt patterns, which are obtained from rotations of the
octahedra with different sense and amplitude about high symmetry axes. We
tabulate all normal modes of each tilt system and specify the contribution of
each atomic species to the mode displacement pattern, elucidating the physical
meaning of the symmetry unique modes. We have systematically generated 705
schematic atomic displacement patterns for the normal modes of all 15 (14
rotated + 1 unrotated) Glazer tilt systems. We show through some illustrative
examples how to use these tables to identify the octahedral rotations,
symmetric breathing, and first-order Jahn-Teller anti-symmetric breathing
distortions of the octahedra, and the associated Raman selection
rules. We anticipate that these tables and schematics will be useful in
understanding the lattice dynamics of bulk perovskites and would serve as
reference point in elucidating the atomic origin of a wide range of physical
properties in synthetic perovskite thin films and superlattices.Comment: 17 pages, 3 figures, 17 tables. Supporting information accessed
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Troublesome toxins: time to re-think plant-herbivore interactions in vertebrate ecology
Earlier models of plant-herbivore interactions relied on forms of functional response that related rates of ingestion by herbivores to mechanical or physical attributes such as bite size and rate. These models fail to predict a growing number of findings that implicate chemical toxins as important determinants of plant-herbivore dynamics. Specifically, considerable evidence suggests that toxins set upper limits on food intake for many species of herbivorous vertebrates. Herbivores feeding on toxin-containing plants must avoid saturating their detoxification systems, which often occurs before ingestion rates are limited by mechanical handling of food items. In light of the importance of plant toxins, a new approach is needed to link herbivores to their food base. We discuss necessary features of such an approach, note recent advances in herbivore functional response models that incorporate effects of plant toxins, and mention predictions that are consistent with observations in natural systems. Future ecological studies will need to address explicitly the importance of plant toxins in shaping plant and herbivore communities
Properties of C in the {\it ab initio} nuclear shell-model
We obtain properties of C in the {\it ab initio} no-core nuclear
shell-model. The effective Hamiltonians are derived microscopically from the
realistic CD-Bonn and the Argonne V8' nucleon-nucleon (NN) potentials as a
function of the finite harmonic oscillator basis space. Binding energies,
excitation spectra and electromagnetic properties are presented for model
spaces up to . The favorable comparison with available data is a
consequence of the underlying NN interaction rather than a phenomenological
fit.Comment: 9 pages, 2 figure
Application of phenotypic microarrays to environmental microbiology
Environmental organisms are extremely diverse and only a small fraction has been successfully cultured in the laboratory. Culture in micro wells provides a method for rapid screening of a wide variety of growth conditions and commercially available plates contain a large number of substrates, nutrient sources, and inhibitors, which can provide an assessment of the phenotype of an organism. This review describes applications of phenotype arrays to anaerobic and thermophilic microorganisms, use of the plates in stress response studies, in development of culture media for newly discovered strains, and for assessment of phenotype of environmental communities. Also discussed are considerations and challenges in data interpretation and visualization, including data normalization, statistics, and curve fitting
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Modifier Genes as Therapeutics: The Nuclear Hormone Receptor Rev Erb Alpha (Nr1d1) Rescues Nr2e3 Associated Retinal Disease
Nuclear hormone receptors play a major role in many important biological processes. Most nuclear hormone receptors are
ubiquitously expressed and regulate processes such as metabolism, circadian function, and development. They function in
these processes to maintain homeostasis through modulation of transcriptional gene networks. In this study we evaluate
the effectiveness of a nuclear hormone receptor gene to modulate retinal degeneration and restore the integrity of the
retina. Currently, there are no effective treatment options for retinal degenerative diseases leading to progressive and
irreversible blindness. In this study we demonstrate that the nuclear hormone receptor gene Nr1d1 (Rev-Erba) rescues Nr2e3-
associated retinal degeneration in the rd7 mouse, which lacks a functional Nr2e3 gene. Mutations in human NR2E3 are
associated with several retinal degenerations including enhanced S cone syndrome and retinitis pigmentosa. The rd7
mouse, lacking Nr2e3, exhibits an increase in S cones and slow, progressive retinal degeneration. A traditional genetic
mapping approach previously identified candidate modifier loci. Here, we demonstrate that in vivo delivery of the candidate
modifier gene, Nr1d1 rescues Nr2e3 associated retinal degeneration. We observed clinical, histological, functional, and
molecular restoration of the rd7 retina. Furthermore, we demonstrate that the mechanism of rescue at the molecular and
functional level is through the re-regulation of key genes within the Nr2e3-directed transcriptional network. Together, these
findings reveal the potency of nuclear receptors as modulators of disease and specifically of NR1D1 as a novel therapeutic
for retinal degenerations
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